In online tutorial communities, it is not uncommon to find problems that include questions like “what is the solution I am looking for?"https://stats.stackexchange.com/questions/66766/. Automated hints such as help with identifying the unknown, could provide timely support to self-directed learners  [1]}, [2]}, [3]}. Furthermore, information about the unknown can be used as a feature in other tasks that can enhance self-directed learning, such as similar-question retrieval  [4]}, and question-answer matching [5]}, as well as in models for automated problem solving [6]}.
